Dry cell



Apri1`14,1942. H. E. LAW'SQN 2,219,515

DRY CELL.

Filed Dec. 13, 1939 @deze for.'

Patented Apr. 14,1942

UNITED STATES] PATENT ori-lcs Herbert E. Lawson, Chicago, Ill.,

Burgess Battery Company, Chicago, poration of Delaware assitnor to Ill.,a cor- Appneauon December 13, 1939, serial No. 308,923

(ci. 13s- 154) 6 Claims.

This invention relates to dry cells, and particularly to improvements inthe construction whereby deterioration of such cells during periods ofstorage and inactivity is reduced.

It is the object of the invention to provide an improved dry cell whichhas favorable "shelf life and intermittent drain properties.

Briefly, the improvement is obtained by associating a wood balsam withthezlnc anode of the cell in such way as to be eiective at the surfacethereof which is exposed to the electrolyte. In accordance with theinvention, it has been discovered that the wood balsams,'as a class ofma.-

y storage, in the plant or on the dealers shelf, for -y between the timethey are Cil a considerable period manufactured and the time they areplaced in use by the consumer. After they are placed in use, they may bedischarged rapidly, or they mayV be discharged slowly and onlyintermittently, with relatively long periods of inactivity interveningbetween periods of use. It is highly important, therefore, that a drycell does not deteriorate and lose its capacity to deliver 'electricenergy during such inactivity. Unless steps are taken to resist suchdeterioration, it takesplaceat an Iappreciterials, possess the propertyof inhibiting the corrosion of the zinc anode, which, due to localaction or other causes, occurs during periods of inactivity.

The invention will be described `in connection with the commoncylindrical type of dry cell. It is not limited to this type of cell,however, and may be used with any dry cell in which a zinc anodeis-employed in such manner as to have a surface thereof exposed to anelectrolyte. The dry cell which is illustrated in the drawing comprisesan open-top cylindrical zinc can i@ which is the negative electrode.Upon the bottom of the can is disposed a layer of electrical insulatingmaterial Il, which may be a heatfusible pitch or wax composition, aresin, or a treated fibrous material such as paper board or pulp board,

which is resistant to the electrolyte of the cell.

A carbon, rod positive electrode l2 is disposed substantially centrallyof the zinc can lo and has a metal cap I3 upon its upper end. The carbonrod is electrically insulated and positively separated from the bottomof the can Ill by the insulating layer ll.- The carbon rod is surroundedby a moist, compacted mass of depolarizing material i4 which may becomposed of powdered manganese dioxide ore, carbon or graphite, ammoniumchloride, zinc chloride, and other wellknown ingredients. Between thedepolarizing body l and zinc can l0 is a substantially solid,electrolyte-containing layer l5 which may be composed of the usualelectrolyte substances, such as water, starch, usually in gelatnlzedform, ammonium chloride, zinc chloride, etc. The electrolyte is in theform of an aqueous solution when initially inserted in the can Id. A topwasher i6 is arranged in spaced relation above the depolarizing body I4to form an expansion'spce I1, and

able rate, and the dry cell industry has from the beginning striven toovercome this difficulty. This invention provides an improvedmeans foraccomplishing the purpose.

In accordance with this invention, it has been discovered that woodbalsams have the property ,to a remarkable degree of inhibitingcorrosion of the zinc electrode during inactivity of the cell, bothbefore and after the cell is initially placed in use. They do not,however, interfere with the delivery of energy while the cell is inoperation. It is a primary feature of the invention to llncorporate amaterial of this character in the electrolyte layer l5 contiguous to thedry cell can' Ill. The wood balsams which are available upon the marketmay be used for the purpose. A large number of balsams-have been usedwith success, among them being the following: balsam copaiba, Oregon firbalsam, gumbo limbo balsam,

` balsam Peru, balsam Mecca, Canada balsam,

a. heat-fusible seal I8, of wax or pitch, rests upon Cil Cuban pinebalsam, citrus guinosa balsam, resinoid Sandalwood and resinoidpatchouli. Other wood balsams may be used, and it is understood that theinvention is not limited to those specifically mentioned.

The balsams are in the form of solids or liquids, and may beincorporated in the dry cell in V several different ways. The simplestmethod is to deposit a small quantity of the material upon the top ofthe depolarizing body I4 or electrolyte paste l5. A portion of itbecomes absorbed by the depolarizing body or electrolyte paste andspreads to the surface of the zinc can l0.. It becomes distributedvuniformly and protects the entire area of the zinc whichl is exposed tothe electrolyte.

The balsam may also be incorporated in `the form of a suspension ordispersion thereof in the electrolyte. It may be added to theelectrolyte liquid with agitation before the electrolyte is inserted inthe can l0. It is adsorbed by the starch present in the electrolyte, andthis promotes its uniform distribution. To'im'prove the thoroughdispersion of the balsam, an emulsifying agent. such as an organic aminemay be added. Triethanolamine is an example. 'A small vquantity ofammonia added-to the liquid also serves the purpose. c

Satisfactory results are also obtained by rinsing the interior surfaceof the zinc can with a dilute solution or emulsion of the balsam, or

by dipping the can momentarily into such a so-` lution or emulsion,before the other elements of the cell are inserted in the can.

In a. well known type of dry cell, the electrolyte layer I5 is in theform of a lining'of paper pulp sheet material which is inserted in thecan I 0 and is saturated with electrolyte. The balsam may be applied tothe paper pulp -sheet before it is insertedin the can, or it may beincorporated in the liquid electrolyte before the latter is inserted inthe can.

'Ihe amount of balsam which should be used' `is not critical.

A relatively small lamount is all that is required. 'I'his depends uponthe specific balsam used. In a dry cell adapted for heavy duty, such asmeter readers service, employing a zinc can 21A inches high and 1%inches in diameter, approximately 0.16 gram oforegon r balsam has beenused inthe electrolyte paste4 of each cell with satisfactory results.lHowever, more than this may be used and, in general, more is used incells intended for light,.intermittent service than in those intendedfor heavy duty. So much balsam should not be used aswill cause theinternal resistance of the cell to be exces- The reason for theremarkable beneficial results produced by the use of a Wood balsam isnot fully understood. c 'Ihe balsams are partially soluble in water, andit may be thatvthe beneficial results are producedfbi? $01112 chemicallyactive agent'which goes into solution inl the liquid of the electrolyte.It may be that they are produced by the formation of a mechanical layeror film of the balsam upon the surface of the zinc. It is`believed thatthe active agent, whatever it is, is physically present at the surfaceof the zinc and exerts its influence there. This presence may be due tomigration Vfrom differcnt localities within the cell, as where thebalsam is incorporated in the electrolyte; or to actual application tothe zinc surface, as where lthe can is rinsed with' an emulsion orsolution of the balsam. The distribution of the substance over theactive surface of the zinc is thorough even when a small amount of the.natural balsam is placed directly upon the top of the depolarizing bodyor electrolyte paste, because in such case the entire active surface ofthe zinc is protected effectively against deterioration and Icorrosion.Therefore, the invention contemplates the application of the balsam tothe interior of the cell in any manner whereby it has an opportunitytobecome accessible to the zinc and is eni abled to exert its beneficialeffect.

sam, citrus gumosa balsam, reslnoid SandalwoodA and resinoid patchouli.

3. In a dry cell having a zinc anode, and a y non-alkaline chlorideelectrolyte adjacent said anode; a suspension of wood balsam at thesurface of said anode exposed to said electrolyte.

4. In a dry cell having a zinc anode, and a non-alkaline chlorideelectrolyte adjacent said anode; a suspension of wood 'balsam at thesurface of said` anode exposed to said electrolyte, said wood balsambeing Ifrom the group consisting of balsamcopaiba, Oregon rbalsam, gumbolimbo balsam, balsam Peru, balsam Mecca, Canada balsam, Cuban pinebalsam, citrus gumosa balsam,` resinoid Sandalwood and resinoidpatchculi.

5. A non-alkaline chloride electrolyte for a dry cell containing a Woodbalsam in suspension therein.

6. The method for decreasing the corrosion during inactivity of the zincelectrode of a dry cell having a non-alkaline chloride electrolyte,which comprises applying asuspensicn of wood l balsam to the' surface ofthe zinc exposed to the electrolyte.

HERBERT E. LAWSON.

balsam being from

